So, I filled my car up full on Chevron 93, same as usual. Take the car out and it performs like it always did.

After about 30min of driving I park. Stand around with a group for 20min or so and then start it up and pull it around back of this biulding for some pictures with a friend. I leave it idling and within a few seconds it just dies... no sputter.. just... quits. Starts back up just fine. But then I notice.. the A/F starts out wround 14.8, then climbs to 15's then to the 16's! As I'm sitting there watching it it bounces around in the 16's a bit and then touches into the 17's and dies... Wait awhile, start it back up and it does the same thing and has a hard time idling. I'll rev it up slightly and the RPMs fall, bounce around from 600RPMs back up to around 900 and then settle out at the usual 700ish. When driving it does just fine, no problems, its steady at around 14.8 A/F and even at WOT does just like it always has...

Its got the Procharger on it, stock pulley, basic "out of the box setup" with 380cc injectors and GReddy EU.

Is the MAF dirty? Clogged filter?

Oh yeah, and someone did tell me that Houston got a bad batch of gas here lately... so I wonder if that station got some?

 

only way to find out , is get rid of the gas thats in there now

 

Bluh... $50 bucks down the drain... And the one time I decided to fill it to the rim...

 

Could be a vac leak with the AFR going lean at idle like that but WOT AFR being normal. Bad gas wouldn't explain the AFR being funky.

 

My car had the same problem. AFR's just went wild for no apparent reason. Found out the culprit was the MAF going bad. Not sure if it applies to you also.

 

I had similar issues when I blew the main boost tube off the throttle body... except the AFR was real rich. Engine died, would restart and rev, but die again at idle.

Check for boost or vacuum leaks. That's likely your problem.

 

I had this happen to me yesterday. I was talking to a friend while my car was running. The car started shaking a bit as it struggled to stay running, then it just shut off. i tried to get it going again but it continued having the rough idle problem and my A/F ratio was extremely lean. it got up to 19s. i tried blipping the throttle a bit and it helped a bit but the car still turned off. i waited a few minutes (@5 mins) and started it again, everything has been fine since. made some calls trying to see if i could get some ideas on where to start looking, this is what i was told:
1) one of the injectors possibly went bad (4 or 5)
2) The UTEC went haywire for that moment for some reason, using random parameters

i could not see anything physically wrong with my fuel system or any other part of my Z for that matter.

I had the check engine light on prior for about a day and a half. no biggie as it is usually a random misfire code (P0300). after all this happened i went to go read my codes at a auto store. By the time i got there, the code had gone away on its own like it always has. car continues to run normal.

i am using the stock map (0) on my UTEC, i feel like that one was giving me less problems. I was recently tuned but because of an overboost problem the tune was cut short. i never had this happen until after the tune. not sure what the problem is, perhaps it is a bad tune, MAF or bad gas but until i install the new tube from Turbonetics to fix my overboost problem i will run the stock map (rich as hell at WOT) until i can get tuned again. i will take it real easy until then.

BTW, i am in killeen, Texas now. I had filled up at a Valero in San Antonio, perhaps Texas is getting some crappy gas

 

perhaps this has something to do with it

https://my350z.com/forum/forced-induction/185829-shimming-cas-to-get-utec-working.html

 

I think it is bad gas this also happened to me once I went to moroso and pumped gas up their for the trip back home after driving a while ill punch the car at WOT same thing as you when I stopped car was shaking due to insufficient mixture and it would turn off.

 

Good read in the other thread - thanks for the link! But I'm also auto, could the crank sensor still be a problem? SGP is about to install bigger injectors and a return fuel system, I'm gonna go ahead and get a new filter and also get a MAF from work just incase. I usually only drive the car on the weekends so I guess I could start it back up and see if it acts up again on the way to SGP...

Thanks for all the help! I guess we'll try and get it figured out!